Date: Sat, 19 Sep 2020 17:25:06 -0700 From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: freebsd-hackers@freebsd.org, freebsd-current@freebsd.org Subject: [PATCH] libm -- optimize __ldexp_cexp[f] Message-ID: <20200920002506.GA47948@troutmask.apl.washington.edu>
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The following patch is an opimization for he kernels
used by cexp(x) and cexpf(x).
. Use sincos[f] instead of a call to cos[f] and a
call to sin[f].
. While here, alphabetize declaration.
--- /usr/src/lib/msun/src/k_exp.c 2019-02-23 07:45:03.879997000 -0800
+++ src/k_exp.c 2019-12-26 08:15:30.109189000 -0800
@@ -88,7 +88,7 @@
double complex
__ldexp_cexp(double complex z, int expt)
{
- double x, y, exp_x, scale1, scale2;
+ double c, exp_x, s, scale1, scale2, x, y;
int ex_expt, half_expt;
x = creal(z);
@@ -105,6 +105,7 @@
half_expt = expt - half_expt;
INSERT_WORDS(scale2, (0x3ff + half_expt) << 20, 0);
- return (CMPLX(cos(y) * exp_x * scale1 * scale2,
- sin(y) * exp_x * scale1 * scale2));
+ sincos(y, &s, &c);
+ return (CMPLX(c * exp_x * scale1 * scale2,
+ s * exp_x * scale1 * scale2));
}
--- /usr/src/lib/msun/src/k_expf.c 2019-02-23 07:45:03.881215000 -0800
+++ src/k_expf.c 2019-12-26 08:15:30.109818000 -0800
@@ -71,7 +71,7 @@
float complex
__ldexp_cexpf(float complex z, int expt)
{
- float x, y, exp_x, scale1, scale2;
+ float c, exp_x, s, scale1, scale2, x, y;
int ex_expt, half_expt;
x = crealf(z);
@@ -84,6 +84,7 @@
half_expt = expt - half_expt;
SET_FLOAT_WORD(scale2, (0x7f + half_expt) << 23);
- return (CMPLXF(cosf(y) * exp_x * scale1 * scale2,
- sinf(y) * exp_x * scale1 * scale2));
+ sincosf(y, &s, &c);
+ return (CMPLXF(c * exp_x * scale1 * scale2,
+ s * exp_x * scale1 * scale2));
}
--
Steve
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